Intramolecular Alkyne Aromatization: Unexpected Synthesis of Expanded [9]Helicene and π‐Extended Double [4]Helicene, and Their Molecular Geometry Effect on Transistor Memory

Intramolecular alkyne aromatization is a powerful tool that enables the synthesis of nonplanar polycyclic aromatic hydrocarbons. Herein, an unexpected intramolecular via trifluoroacetic acid-promoted cyclization described, in which two structural isomers, expanded [9]helicene (1) and π-extended double [4]helicene (2) are obtained. A possible rearrangement mechanism proposed to account for formation 1. The geometric optoelectronic properties these molecular nanocarbons comprehensively investigated by single-crystal X-ray, UV–vis absorption, photoluminescence spectra, cyclic voltammetry analysis. These isomers exhibit wide energy gaps with similar levels, further apply them as floating gate organic field-effect transistor nonvolatile memory (OFET-NVM) devices. geometry 1 2 shows remarkable effect on charge-trapping behaviors OFET-NVMs; 1-based device displays more than threefold wider window (MW, 44.5 V) 2-based (14.2 V), large density 1.08 × 1013 cm−2. distinct different behavior likely attributed geometries, resulting molecular-packing modes. It revealed this study controlling new strategy application electronics.